Stanford University researchers have developed a 3D printing technique which could enable scientists to study rocks from afar without requiring samples. The method can also be used to study the relationship between a rock’s microscopic and large-scale properties.

Tiziana Vanorio and Dulcie Head with their Formlabs 3D printer

Scientists, whether they happen to be specialists in geophysics or not, have long been keen to find out exactly what rocks are like on the Moon and on Mars. For obvious reasons, however, it can be difficult to obtain large quantities of samples from such places, leading researchers to approach new methods of studying the far-flung materials. A team of Stanford researchers has devised a new technique, a combination of remote 3D imaging and 3D printing, which could help scientists study the properties of rocks without actually having samples to hand.

According to Tiziana Vanorio, an assistant professor of geophysics at Stanford’s School of Earth, Energy & Environmental Sciences, 3D printed digital rock models could someday be used to screen and select the most relevant samples from the Moon and Mars to be returned to Earth. Until then, however, the technology can also be used in another important way: to study how a rock’s microscopic structure affects its large-scale properties, such as its porosity and permeability, which can often function as signifiers as to how a rock was formed and how fluids might pass through it. This kind of information can then be used inform more efficient extraction techniques.

After purchasing a pair of customized, 3D printed ballerina shoes a few years ago, Vanorio realized that the scan-then-print model could be replicated on rock samples. “The advent of modern 3D printing provides an unprecedented opportunity to link the micro and macro scales by combining the strengths of both digital and laboratory experiments,” Vanorio said. “3D printing allows us to digitally manipulate changes at the pore scale and then print the rock at the scale that is suitable for laboratory tests.”

While researchers have used 3D printing on rocks before, the Stanford researchers are breaking new ground by using additive manufacturing technology to digitally modify the microscopic structures of those rocks in order to test how the changes affect fluid flow. In their study, the team used a high-end commercial 3D printer (a Formlabs Form 1) and a ten-times-as-expensive industrial model to print 3D rock models obtained from a CAT scan. Both Stereolithography-style printers were able to 3D print the rock structures. However, the more expensive machine, which used wax-assisted technology, could create smaller pore spaces, resulting in more accurate recreations of the microscopic channels and hollows in the small carbonate rock sample.

Stanford doctoral candidate Dulcie Head

“A fundamental problem for geophysicists who want to understand rock properties is that our samples are not naturally comparable,” said Dulcie Head, a Stanford doctoral candidate in Vanorio’s lab. “You can take two rock cores from right next to each other that have very similar bulk properties, but when you look at them under a microscope, their pore structures might be completely different. By manipulating something that we couldn’t manipulate before, 3D printing allows us to understand the role of those tiny differences in the pore structure.”

Using the two 3D printers, the Stanford researchers were able to show that a digital model of a rock can be altered and 3D printed, enabling scientists to study how changes in a rock’s microstructure relates to its “bulk” properties. Despite the initial success, however, the project is still in its infancy. As 3D printing technology improves, it will be possible to print finer and finer details of a rock’s microstructure and even mix several materials together in order to more realistically replicate different forms of mineral. While the researchers used curable resin for their initial 3D printed samples, they could turn to 3D printable glass, metal, and ceramic materials for future studies.

Vanorio and Head’s research has been published in Geophysical Research Letters, and was also selected as an Editor’s Choice study by the journal Science.